Bently Nevada Eddy-Current Proximity Systems: 5 mm to 11 mm Solutions for Reliable Machine Protection

More than six decades ago, Don Bently introduced the first industrial eddy-current proximity sensor. Since then, the portfolio has expanded to include 3300 XL 5 mm, 8 mm, and 11 mm probes that deliver laboratory-grade accuracy inside turbines, compressors, and pumps. Every sensor is fully API-670 compliant and CE-certified, converting shaft motion into high-resolution electrical signals without contacting the target. The result is zero mechanical wear and a service life that far exceeds traditional switches or velocity pickups.

The Bently Nevada proximity family covers every common machine geometry. The 3300 XL 5 mm Proximity Probe, Sensor and Transducer System includes the 3300 5mm probe, 3300 XL 5mm extension cable, and 3300 XL 5mm proximity sensor for tight-clearance compressors. The 3300 XL 8mm Proximity Probe, Sensor and Transducer System combines the 3300 XL 8mm proximity probe, 3300 XL 8mm extension cable, and 3300 XL 8mm proximity sensor to meet API-670 standards on general-purpose steam and gas turbines. For large, slow-speed shafts, the 3300 XL 11mm Proximity Probe, Sensor and Transducer System offers the 3300 XL 11mm probe, 3300 XL 11 mm extension cable, and 3300 XL 11mm proximity sensor, delivering four millimetres of linear range and tolerance to heavy oil films.

Each 3300 XL system consists of three matched components. The 3300 XL 5 mm, 8 mm, or 11 mm hermetically sealed proximity probe carries an armored cable rated from –52 °C to +100 °C. The corresponding 3300 XL extension cable is offered in fixed-length or custom-cut versions and is color-coded for immediate gap verification. The 3300 XL Proximitor sensor provides signal conditioning, 4-hole panel or DIN-rail mounting, electrical isolation, and SpringLoc terminals that eliminate screwdrivers. Factory-supplied calibration curves maintain ±2 % accuracy when components are swapped in minutes.

Early orbit and thrust-position alarms convert unplanned outages into scheduled repairs, cutting downtime by up to forty percent. Insurance carriers recognize API-670 installations as reduced-risk assets, often lowering premiums. Stable gap voltage removes phantom trips that waste fuel and product, so throughput and quality rise simultaneously. Mean time between failure exceeds five hundred thousand hours per IEC 60529, reducing spare-parts inventory and freeing working capital.

Small centrifugal compressors with limited radial clearance use the 3300 XL 5 mm probe on aluminum or steel targets. Steam and gas turbines follow API-670 guidelines and employ the 3300 XL 8 mm version, which delivers 1.5 mm of linear range and requires a minimum shaft diameter of forty-five millimeters. Large slow-speed gearboxes and paper rolls benefit from the 3300 XL 11 mm probe, whose 4 mm range accommodates heavy oil films and run-out greater than eight tenths of a millimeter. The largest probe that fits the physical space is generally the best choice because the increased tip diameter averages surface imperfections and produces a smoother signal.

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